Thermionic tube



.Dec. 22, 1931. o. T. MclLvAlNE 1,837,566

THERMI ONI C TUBE Original Filed July 2. 1925 Figa i Patented Dec. 1931-UNITED STATES-PATENT OFFICE Om T. HcILVAINE, 401E' BT. CHARLES,ILLINOIS, ABBIGNOB T0 vIGILVLAINE PATENT CORPORATION. OF ST. CHARLES,ILLINOIS, A. CORPORATION `OF DELAWARE THEBHIONIC TUBE animan mea my a,1925, semi 1ra. 41,070. acne'wea any 1s,'1aa1.

This invention relates to'thermionic tubes such as are employed in thereception, detection, -amplification and repeating of sounds and signalsas in wireless, radio, telephone,

and the like and has for its objects the provision of anew and improvedtube which shall be much more sensitive to incoming electric signalsandmuch less sensitive to mechanical shocks and blows than previous devicesof this nature and shall exhibit a current without a tral sectional viewthrough an improved radio tube embodying my improvements;

' Fig. 2 is a similar view through a modified form of tube; and Fig. 3is a perspective view with parts broken away showing the preferredconstruction of tube elements.

My improved tube comprises the usual evacuated glass globe in which thetube elements are mounted. In Fig. 1 I have shown a double ended tubularcontainer or globe 1 made of glass, that is to say, each end of a glasstube is closed by a press, 2 or 3, and each end of the container soformed outside of the press is provided with a. base member of suitabledesign. In the present case I have shown the globe or container .asprovided at the end having the press 2 with a screw-threaded base 4adapted for the reception of the standard socket employed in electrichouse lighting. Inside the globe the press 2 carries, suitably insulatedthermally, a small parabolic reflector 5 inside of which,

adjacent the parameter, is an incandescent electric resistance wire 6preferably coiled into a thin coil so that the heat and light rays castby the reflector may be thrown downwardly in a close, concentrated,intense beam. The end of the globe adjacent the member 4 is covered by ametal cap 7 from which the terminal members are insulated by an inttery,Wave-smoothsulating layer 8. A .wire 9 is preferably secured to thereector 5 and passes through the press 2 where it is preferably formedand adapted for connection to a ground wire (not shown). One modev ofeffecting this construction is to attach the reflector to the cap 7, thelatter being a loop 10 or other provision whereby a ground wire can besecured.

The press 3 at the op site endof the globe or container is prefera lymade of the same size and shape in order to facilitate the doin of thework by automatic machinery, an carried by this press are my new and.improved electron-emitting and absorbing elements. In their preferredform these consist of circular disks of the necessary .materials,located as closely together as is practically convenient and arran ed inthe path of the heat beam cast b sai refiector so as to be heatedthereby wit out electric contact.

/In its preferred form this combination element comprises a circulardisk 12 of some metal which will emit electrons readil at acomparatively low temperature and without becoming modified or injuredby long continued use. Next to the disk is an insulating layer 13 whichpreferably takes the form of a net work of glass or quartz rods,although a series of straight glass threads is sufficient for thepurpose in case they can be held in place. Next to this insulating layeris the grid element, which preferably consists of a screen cloth orforaminous metal sheet 14. Next beyond this is a second 15 which may, ifdesired, be of the same material and dimensions as the layer 13; andfinally is the circular absorption plate or anode 16. .The plate 12 islocated nearest to the heat source and constitutes the cathode, thecathode terminal 17 being connected thereto. The face of this plate onwhich the radiations fall in preferably blackened so as to absorbthelargest possible proportion of this radiation, while its oppositeface is preferably impregnated, either in the metal insulating layerpreferably provided with state or in the combined form with an alkalitothe employment of solid insulating materials in the layers 13 and 15,since it is sufficient for some purposes merely to support themsuiliciently far apart for the air space to separate them, although oneadvantage of my improvements is that by the use of solid insulatingmaterials a device is made which is rigid and proof both against saggingand becoming short circuited with lapse of time and also against theeffect of shocks oi jars. 'lhe grid 14 is connected to the terminal 18and the plate 1G to the anode lead 19, all three of the wires 17, 18,and 19 being fused in the press 3 and thereby supported at the oppositeend from the alternating current connections.

In Fig. 3 l have shown a modification of my tube in which allconnections are at one end of the container which is here shown as bulbshaped. The container 1a has its single mouth closed by the press 2O inwhich are sealed the leading-in wires 21-21 across whose inner ends isconnected the transverse heating element 22. Located in close pronimityto this filament is the combined element as heretofore describedcomprising a cathode plate 12, grid 14 and anode plate 16 withinterposed insulating layers 13 and 15, the plate 12 being located insuch relation to the filament 22 as to be heated by the radiationstherefrom. In this case, instead of employing a reflector behind thefilament and locating the parts at a distance from each other, I havelocated the element and filament close together; and in order to shieldthe operative parts from electro-static influence caused by energizingthe filament by alternating current interpose between the filament andcathode a sheet metal plate 25 separated from the plate 12 merely by athin layer 26 of some substance which conducts heat readily and israther a poor conductor of electricity, the plate 25 being grounded by awire 27 passing through the press. The wires 17, 18, and 19 appear asbefore, although they are shown merely diagrammatically inasmuch as theypreferably lie in planes which do not contain the press.

Owing to the very small distance between the different plates (it willbe understood that the drawings herein shown are of enlarged size andthat a successful element need little, if at all, exceed the dimensionsof a twentylive cent piece) a sufficient electron emission forsuccessful operation can be obtained at comparatively low temperatures,and an eX- tremely small potential is necessary to produce electronmovement, wherefore the device is extremely sensitive, although owing toits small internal resistance its capacity is very considerable. Anadvantage of using a solid insulating substance between the grid and themembers adj acent thereto is that the parts arethereby spaced a fixeddistance from each other, which distance is always maintained regardlessof age, temperature, or nature of use, but neither this substance northe layer 26 need possess any high insulating value inasmuch as it isnever called upon 'to withstand a high potential but a single sheet ofmica or the like is fully ample for the purpose. rThe short distancebetween the grid and plate has the further great advantage of renderingthe tube very insensitive to enternal influences such as that of analternating current in the heating filament, although it will beunderstood that my improved tube can be energized by direct currentequally as well, as by alternating current provided only that the propervoltage be applied.

Having thus described my invention what l claim is:

1. ln a thermionic tube, an anode, a control plate, a cathode, a heatingdevice located in the order named and insulated from each other, saidheating device comprising a radiation element located in radiatingrelation to said cathode and out of conducting relation therewith eitherelectrically or thermally, and a grounded element located in closerproximity to said heating device than to said cathode.

2. ln a thermionic tube, an anode, a con trol plate, and a cathodeassembled togetherl in the order named and an open meshed layer ofelectrically non-conducting solid material interposed between saidcontrol plate and the other members.

3. ln a thermionic tube, an anode, a cathode, means including solidspacing devices of electrically insulating material interposed betweensaid anode and cathode and holding them a fixed distance apart, and anexternal heating device for said cathode located upon the opposite sidefrom said anode, said spacing devices being open meshed to permit thepassage of electrons therethrough.

ft. ln a thermionic tube, the combination with an evacuated globe of ananode and a cathode inside the same, solid spacing devices ofelectrically insulating material between said anode and cathode, and aradiation heating device inside said globe at the opposite side of saidcathode from said anode.

fn 'testimony whereof l hereunto affix my signature.

@RAN T. lvlclLVAlNE.

